The present invention relates general to the field of digital image capture, more particularly to a method of and system for detecting the failure to capture a usable image by a digital camera. The method and system of the present invention find application security systems that capture a digital image. The present invention is particularly adapted for use in an automated postal kiosk environment.
Many systems use cameras for security purposes. Such systems include a relatively inexpensive digital cameras that capture images either at regular intervals or upon the occurrence of an event. The captured images may be stored for later review by a human.
The digital cameras used in security systems may fail to capture an image that is acceptable for identification. For example, the there may be a system failure due to hardware, mechanical, or communication problems. The camera may also fail to capture an acceptable image on account of there being inadequate lighting. Additionally, the subject may defeat the camera by placing an object, such as his hand, over the camera lens. Currently, there is no mechanism for detecting such camera failures.
An example of such a system is an unattended automated postal kiosk, which includes a digital camera. The postal kiosk includes user interface, such as a touch screen display, by which a customer can select a postal transaction type, e.g. Express Mail, Priority Mail, etc., a scale, by which the system may determine the proper amount of postage for the transaction, a payment acceptor, and a postage dispenser. Federal Aviation Administration (FAA) regulations require that the United States Postal Service obtain positive identification from any person that mails a Priority Mail package weighing more than one pound. A standalone kiosk can comply with FAA regulations, and process Priority Mail requests, because it can take a picture of every customer that attempts to mail such a package, and associate the picture with the package. However, currently, the pictures taken at the kiosk are not reviewed by a human unless the FAA requests the picture associated with a particular Priority Mail piece mailed from the kiosk. If there is a failure of the digital camera, then there is a failure of security.
The present invention provides a method of and system for detecting a digital camera failure. The system of the present invention captures an image with the digital camera. The system compresses the image into a compressed image file and compares the size of the compressed image file with a predetermined file size. A small file size implies that there is insufficient color differentiation in the image to make the image usable. A large file size implies that there is extraneous random noise in the image. Thus, according to the present invention, a digital camera failure is indicated if the size of the compressed image file is greater than a predetermined upper limit file size or less than a predetermined lower file size limit. The upper and lower limits are determined empirically. Additionally, the predominance of one particular color in the image implies that the subject has place an object, such as his hand, over the lens of the camera. Accordingly, the system may also compare the number of pixels of a predetermined color with the total number of pixels of the captured image. A digital camera failure is indicated if the number of pixels of the predetermined color is greater than a predetermined percentage of the total number of pixels of the captured image.